The present invention relates generally to computed tomography systems, and more particularly to an apparatus and method for adjusting the resistance of a cathode filament circuit within a computed tomography tube assembly.
Various computed tomography (CT) systems are presently used, each of which have different system functionality requirements. Because of the different functionality requirements, internal CT system components vary depending upon the application, the manufacturer, and a CT system model.
The CT system includes a computed tomography tube assembly including a CT tube and a filament circuit. The CT tube generates X-rays across a vacuum gap between a cathode and an anode. In order to generate the X-rays, a large voltage potential is created across the vacuum gap forcing electrons to be emitted from the cathode to the anode. In releasing of the electrons, a filament contained within the cathode and filament circuit is heated to incandescence by passing an electric current therein. The electrons are accelerated by the high voltage potential and impinge on the anode, whereby they are abruptly slowed down. The impact of electrons produces a large amount of heat. To reduce the amount of heat in the anode the CT tube is oil cooled. Even in so doing, because of the high voltage and heat generated, CT tubes eventually wear out and need to be replaced.
CT systems have varying resistance requirements for the filament circuit. The bulk of the filament circuit resistance is currently from the filament itself. Therefore, each filament has a resistance that is specific to a CT system. When a filament having a certain resistance is installed into a CT system that requires a filament with a different resistance, system errors can occur such as filament shorts that prevent normal system operation. Since tubes are replaced often and are CT system specific, the cost in production and replacement of the various tubes is large.
Also, when improved and updated CT systems are introduced that require a filament resistance which is different from existing filament resistances, further costs are endured to develop and manufacture a new cathode having the newly required filament resistance.
Therefore, it would be desirable to provide an apparatus for adjusting the resistance of an existing cathode instead of designing a new one. The apparatus may provide versatility and interchangeability of CT tubes between CT systems and reduce the number of different cathodes that are produced, thereby saving costs involved in developing and manufacturing of CT tubes.